Two notable studies on Ebola this week shed more light on why some people are devastated by the virus, while others manage to survive the deadly pathogen.

In one, researchers gathered data from 106 Ebola-stricken patients at the Kenema Government Hospital in Sierra Leone from May 25 to July 18. The records of some of the patients were burned due to fears of contamination. But the team was able to thoroughly analyze the data from 44 Ebola patients at the hospital.

"This is the first time anybody has had this much data collected on any Ebola patients,” Dr. John Schieffelin, one of the study’s authors, told Reuters.

The research, published in the New England Journal of Medicine, found that age and the amount of virus in a given patient’s blood appeared to be determining factors in the mortality rate of patients. Researchers reported that 57 percent of people under age 21 who were treated for Ebola died from their infections, compared with 94 percent of those over the age of 45.

In terms of viral load, scientists reported that 33 percent of patients with less virus (less than 100,000 copies of the virus per milliliter of blood) at the time of diagnosis ultimately died, compared with a 94 percent mortality rate in those whose blood contained more than 10 million copies per milliliter.

Overall, 74 percent of the patients in the study died, similar to what has been seen in prior outbreaks.

Genetic influence

In the second study, published in the journal Science, scientists at the University of Washington in Seattle found that laboratory mice, like humans, have a range of responses to the virus.

The team was able to breed mice that developed infections like those found in humans. In the Ebola-infected mice, researchers observed a gamut of outcomes, all the way from minor illness to hemorrhagic bleeding and death.

The scientists identified two genes -- TEK and TIE1 -- in mice that appear to be key in predicting which mouse would die and whether one would become ill at all. In mice that bled, the two genes made their blood vessels weaker and prone to leaking, setting off a chain of responses that caused organs to shut down.

The results may explain why some two-thirds of people who die from Ebola never experience hemorrhaging, findings that were described as a 'significant advance' by Dr. James Musser, a director of infectious disease research at Houston Methodist Research Institute, who was quoted in the New York Times.

The team’s research began three years ago, inspired by its work on the history of the influenza virus, long before the current epidemic in three West African countries.